Fergus Henderson writes:
> Hi,
>
> Is the following legal Haskell?
>
> > infixr 0 `foo`
> > infixr 0 `bar`
> >
> > x `foo` y = "foo(" ++ x ++ "," ++ y ++ ")"
> > x `bar` y = "bar(" ++ x ++ "," ++ y ++ ")"
> > dubious a b c = a `foo` b `bar` c
>
> According to the grammar in the Haskell report, I don't think it is.
> However, ghc-0.24 (ancient, I know) and Hugs 1.3 both accept it without
> complaint.
The report says (pg 13):
Consecutive unparenthesised operators with the same precedence must
both be either left or right associative to avoid a syntax error.
I think, since you have two.... which are both right associative, that
it is fine.
(However, making the lower infixr an infixl should produce a syntax
error. This however does not seem to be the case for hbc)
Jon
